i have a 2015 infinity q50a base model, timing chain issue

Question

i have a 2015 infinity q50a base model, recently started leaking and i run out of oil. now it started slowing down and suddenly it speeds up or slows down and i was told it needs timing chain, what parts do i need to buy from the dealer?
 i have visited almost 4 shops none of them were able to solve the issue and i was about to change the engine, but recently a mechanic guy told me a timing chain is needed for my car and he told me to buy timing chain kit. however after i visited the dealer, i was told that it doesn't sold as one it has many parts and i need to be specific,
can someone help me what parts i might need to order?
and is there a cheaper way to get those parts?
any good mechanic to solve my issue in houston area?
i ended up paying 4 shops diagnosing fee please to fix my car not to check